The present invention relates to a system for transmitting mechanical shaft power in a manner such that the product of the shaft angular speed by the torque transmitted is conserved between an input shaft and an output shaft, assuming that no energy loss occurs within the system. Such mechanisms are also referred to as automatic transmissions in the automobile industry and torque converters in industrial applications. The end results are similar: the ratio of the values of the torques transmitted by the input and output shafts varies as the direct inverse ratio of the angular velocities of said shafts. The power transfer is performed by means of the transformation of mechanical power into hydraulic power, i.e. volumetric flow of incompressible fluid under pressure, and then the process is reversed.
In automatic transmissions, the fluid hydrodynamic power appears in the form of fluid flow rates combined with associated fluid flow velocities. Slippate is inherent to these systems and is more pronounced at low shaft angular speeds. The system efficiency is poor at such regimes of operation. In hydraulic torque converters, the fluid flow velocity is replaced by its equivalence in the form of pressure. However, theoretically, slippage is preventable and the system efficiency is less dependent upon the operating regime of the system. Hydraulic torque converters are not used in the role of automatic transmission for various reasons: cost, ungainly arrangement and weight. The pump component may easily be and generally is separate from the motor component, which offers a flexibility of installation and adaptation to a specific construction.
Efforts are continuously being made to develop variable speed ratio "gearboxes" which provide a continuously adjustable "gear ratio" for application to automobiles. Thus it seems desirable to develop a gearless automatic transmission which takes advantage of the most attractive pertinent features of torque converters. Further, it is desirable to exploit those features which may easily be utilized for optimizing the vehicle operation.
In view of this background, the present invention provides those features, and combinations thereof, that are needed to substantially improve the propulsion of motorized land vehicles. It offers ways to improve fuel consumption and the matching of engine/vehicle characteristics automatically.